Bearing arrangement

ABSTRACT

The invention relates to a bearing arrangement designed as a fixed/floating bearing for a rotor of a fan, having a bearing tube, a compression spring, a shaft arranged coaxially with respect to the bearing tube, and two identically formed ball bearings arranged between the bearing tube and the shaft, each ball bearing having an inner ring and an outer ring, wherein multiple different fit zones are formed axially along the bearing tube, wherein, in a first axial fit zone, one of the ball bearings as a fixed bearing is attached by its inner ring on the shaft and its outer ring is fixed with a press fit on a continuous, shoulder-free portion of the bearing tube and, in a second axial fit zone, another of the ball bearings as a floating bearing is attached by its inner ring to the shaft and its outer ring is axially displaceably arranged with a clearance fit on a continuous, shoulder-free portion of the bearing tube, wherein the compression spring is arranged in a third axial fit zone and, exerting a preload against the outer rings of the ball bearings, is positioned axially between the ball bearings and is designed to eliminate bearing play of the floating bearing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 U.S. National Phase of InternationalApplication No. PCT/EP2019/062392, filed May 14, 2019, which claimspriority to German Patent Application Numbers 10 2018 129 613.4, filedNov. 23, 2018; 10 2018 129 611.8, filed Nov. 23, 2018; and 10 2018 129608.8, filed Nov. 23, 2018. The entire disclosures of the aboveapplications are incorporated herein by reference.

FIELD

The disclosure relates to a bearing arrangement designed as afixed/floating bearing for a rotor fan.

SUMMARY

In prior art uses, bearing tubes have fixed/floating bearingarrangements with floatingly projecting shaft loads. As a rule, abearing tube with an inner shoulder or a geometrical shoulder, foradjoining a bearing, is provided for bracing the bearings in anO-arrangement. The first bearing is inserted into the bearing tube fromone axial side. A spring and the second bearing are inserted from theother axial side. Both inner rings of the bearings are fixedly connectedto be mounted to the shaft. The bearing assembly is self-supporting upto the amount of the preload. If the outer ring of the first bearing isfor example fixed by caulking, gluing, or a retaining ring, the mountingis defined in all directions.

The bearings are machined and inserted from two sides in such bearingtubes. In addition, a geometrical bearing shoulder must be provided,which is not always desired. Furthermore, the coaxiality of the bearingseats is not optimal with two-sided machining.

It is an underlying problem of the disclosure to provide a bearingarrangement for a rotor fan that features improved coaxiality of thebearing seats and a simplified assembly option from a single axial side.

This problem is solved by the combination of features including abearing arrangement designed as a fixed/floating bearing for a fan rotorcomprising a bearing tube, a compression spring, a shaft arrangedcoaxially with respective to the bearing tube, and two identicallyformed ball bearings arranged between the bearing tube and the shaft.Each ball bearing has an inner ring and an outer ring. Multipledifferent fit zones are formed axially along the bearing tube. A fixedbearing, is attached by its inner ring on the shaft and its outer ringis fixed with a press fit on a continuous shoulder-free portion of thebearing tube. In a second axial fit zone, another of the ball bearingsas a floating bearing, is attached by its inner ring to the shaft andits outer ring is axially displaceably arranged with a clearance fit ona continuous, shoulder-free portion of the bearing tube. The compressionspring is arranged in a third axial fit zone. The compression spring ispositioned axially between the ball bearings exerting a preload againstthe outer rings of the ball bearings to eliminate bearing play of thefloating bearing.

According to the disclosure, a bearing arrangement, designed as afixed/floating bearing for a rotor fan, is proposed with a bearing tube,a compression spring, a shaft arranged coaxially with respect to thebearing tube and two identically formed ball bearings arranged betweenthe bearing tube and the shaft. Each ball bearing has an inner ring andan outer ring. Multiple different fit zones are formed axially along thebearing tube. In a first axial fit zone, one of the ball bearings, as afixed bearing, is attached by its inner ring on the shaft. Its outerring is fixed with a press fit on a continuous shoulder-free portion ofthe bearing tube. In a second axial fit zone, another of the ballbearings, as a floating bearing, is attached by its inner ring to theshaft. Its outer ring is axially displaceably arranged with a clearancefit on a continuous shoulder-free portion of the bearing tube. Thecompression spring is arranged in a third axial fit zone. It exerts apreload against the outer rings of the ball bearings. The spring ispositioned axially between the ball bearings and is designed toeliminate bearing play of the floating bearing. To this end, thecompression spring is selected such that it has a sufficient springforce for the respective bearings.

The solution according to the disclosure does without geometricalshoulders or bearing shoulders on the bearing tube for the bearings. Thepresent disclosure provides different fit zones for the two bearings,one as a press fit and one as a clearance fit. This enables completelyone-sided machining and assembly of the bearings. Furthermore, thecoaxiality of the two bearing seats is optimized.

Assembly is simplified because the fixed bearing, the compressionspring, and the floating bearing can be inserted from the same side andonly pressing processes that can easily be monitored can be used. Also,no additional parts, such as retaining rings, or additional materials,such as adhesive, are required.

The different fit zones are preferably determined by different tolerancezones of the inner diameter of the bearing tube. The regions of thecompression spring and the floating bearing feature a clearance fit withthe outer ring. The region of the fixed bearing features a press fitwith the outer ring of the bearing. The bearing arrangement uses anO-arrangement braced on the outer ring.

In one embodiment of the bearing arrangement, the third axial fit zonecorresponds to the second axial fit zone in the region of thecompression spring. Thus, only two different fit zones are provided. Theclearance fit in the region of the spring can have a greater tolerancethan the one of the floating bearing.

Furthermore, in an advantageous embodiment of the bearing arrangement,an axial fit length L1 of the first fit zone of the fixed bearing isdefined as 0.35∩L1≤D≤0.5⋅L1. Here D is an inner bearing tube diameter ofthe bearing tube. In addition, an axial fit length L2 of the second fitzone of the floating bearing is defined as 0.35⋅L2≤D≤0.5⋅L2. This shortaxial length of the fit zones reduces required machining to small axialsections. The third fit zone of the compression spring is always locatedaxially between the two fit zones of the press fit and clearance fit ofthe two ball bearings.

In a further development of the bearing arrangement, the first and thesecond fit zones each adjoin axial edge sections of the bearing tube.Their position is thus unique and easily determined.

The entire axial holding force must be borne by the press fit of theouter ring of the fixed bearing with the bearing tube. To ensure thisover a wide temperature range, a material is selected for the bearingtube that has an expansion coefficient very similar to the material ofthe outer rings of the ball bearings. In a preferred embodiment, thematerial of the outer rings of the ball bearings is even identical to amaterial of the bearing tube, for example, steel.

In a favorable solution, the outer rings of the ball bearings and thebearing tube are formed of soft magnetic steel. This is due to the factthat non-magnetic, austenitic steels have a too high expansioncoefficient.

The expansion coefficient is of subordinate importance for the shaft tobe mounted and may deviate from that of the bearing tube. But it isdefined such that it is similar to the expansion coefficient of theinner ball bearing rings and that the press fit is not impaired andthere is no impermissible radial change of air of the ball bearing.

For use in a fan, an embodiment of the bearing arrangement isadvantageous where a projection is formed on an axial end section of thebearing tube and integral with the bearing tube. The projectioncomprises a receiving space for inserting a fan wheel. Thus the bearingtube, in addition to its bearing function, can define a receptacle forthe fan wheel and contribute to a compact design requiring littleinstallation space and a small number of parts. The disclosure thereforealso related to a fan having the bearing arrangement described above.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

Other advantageous further developments of the disclosure are presentedin the dependent claims or are explained in more detail below withreference to the figures and together with a preferred embodiment of thedisclosure.

FIG. 1 is a perspective cross-sectional view of a bearing arrangement ofa rotor of a fan;

FIG. 2 is a perspective cross-sectional view of a bearing arrangement ofa rotor of a fan; and

FIG. 3 is a cross-sectional view of a fan with a bearing arrangement.

DETAILED DESCRIPTION

FIGS. 1 and 2 show two exemplary embodiments of bearing arrangements 1designed as fixed/floating bearings for a fan rotor 11.

Referring now to FIG. 1, it shows a perspective sectional view of thebearing arrangement 1 with the bearing tube 2, a shaft 28 of a drivemotor arranged coaxially with the bearing tube 2, of which motor onlythe rotor 11 is shown.

Two identically configured ball bearing 3, 6, each with an inner ring 4,7 and an outer ring 5, 8, are arranged between the bearing tube 2 andthe shaft 28. One of the bearings is used as a fixed bearing and theother one as a floating bearing. The compression spring 9, which exertsa spring force to eliminate the bearing clearance against the two outerrings 5, 8, is located axially between the two ball bearings 3, 6.

Different fit zones are formed due to different tolerance zones on theinner wall surface of the bearing tube 2 in the region of the two ballbearings 3, 6.

In a preferred exemplary embodiment, the fit of the two bearings due todifferent tolerance zones of the diameters are implemented as follows:

Diameter of the shaft=4.002-4.005 mm

Diameters of the inner rings 4, 7=3.995-4.000 mm

Diameters of the outer rings 5, 8=10.995-11.000 mm

Diameter of the bearing tube for ball bearing 6 (fixedbearing)=10.983-10.993 mm

Diameter of the bearing tube for ball bearing 3 (floatingbearing)=11.000-11.011 mm

Diameter of the bearing tube in the region of the compression spring9=11.000- 11.04 mm

The geometrical dimensions are adjusted accordingly for greater orsmaller embodiments.

The ball bearing 6 is configured as a fixed bearing, the ball bearing 3as a floating bearing, but this arrangement may also be reversed. Theinner ring 7 is fastened to the shaft 28. The outer ring 8 is fixed to acontinuous shoulder-free section of the bearing tube 2 by means of apress fit. No bearing shoulder or any other geometrical shoulder isprovided on the inner wall surface of the bearing tube 2. The bearingtube 2 extends continuously without a step in the axial direction. Thus,all components can be mounted from a single axial side. The second,identically configured ball bearing 3 is a floating bearing and likewisefastened with its inner ring 4 to the shaft 28. The outer ring 5 is alsoarranged in an axially movable manner and, with a clearance fit, on acontinuous shoulder-free shoulder of the bearing tube 2. The third fitzone is provided in the axial region of the compression spring 9 betweenthe two ball bearings 3, 6. In the exemplary embodiment shown, this zonecorresponds to the fit zone of the ball bearing 3 defining the floatingbearing, such that only two different fit zones are provided. The thirdfit zone in the region of the compression spring 9 can be variablyadjusted and may differ from the two fit zones of the ball bearings 3,6.

In the exemplary embodiment shown, the axial fit length L1 of the firstfit zone of the ball bearing 6, defining the fixed bearing, and thesecond fit zone of the ball bearing 3, defining the floating bearing, isfurther defined as 0.4 of the inner bearing tube diameter of the bearingtube 2. Both fit zones each directly adjoin the axial edge sections ofthe bearing tube 2.

In the exemplary embodiment according to FIG. 1, a collar 25 formedintegrally with the bearing tube 2 is configured on the upper axial endsection of the bearing tube 2, which collar defines the receiving space87 for inserting the fan wheel 17.

The exemplary embodiment according to FIG. 2 has the same features asthe one from FIG. 1. However, it differs in that the collar 25 is notprovided on the bearing tube 2 but as a separate component. In theembodiment shown, the collar 25 is formed by a flow divider that isdescribed in more detail with reference to FIG. 3.

FIG. 3 shows a sectional view of a radial fan 100 with the bearingarrangement 1 from FIG. 1. The radial fan 100 includes an electric motor92 configured as an encapsulated motor with a rotor 11 and a stator 32.The magnets of the rotor 11 are attached to the shaft 28 that extendsaxially along the axis of rotation through the radial fan 100. The fanwheel 17 configured as a radial fan wheel is fastened to the shaft 28The fan wheel 17 when in operation, takes in air by means of itsimpeller vanes axially through the inlet 69 and blows out air via thedischarge nozzle 33 at the outlet 44. The radial fan 100 furtherincludes the fan housing, which is formed by the outer part 40, theinner part 50, and the housing cover 19, where the motor 52 isaccommodated. The circuit board 110 with electronics components fixedthereon for regulating the radial fan 100, is attached axially betweenthe inner part 50 and the motor 52 and to the housing cover 19. Theinner part 50, on the one hand forms a free space for the electronicscomponents on a side facing the motor 52. On the other hand, the innerpart 50 defines, together with the outer part, the helical pressurespace D on the opposite axial side of the radial fan 100 facing theouter part 40. The inner part 50 extends radially outwards between theouter part 40 and the housing cover 19 and is fixed by the outer part 40and the housing cover 19. Seals 25 are provided to seal off the twoaxial regions separated by the inner part 50. The electronics componentsare arranged in the free space adjacent to the pressure space D. Thus,the electronic components face the flow, whereby heat is dissipated tothe inner part 50 and cooling takes place.

The annular flow divider 18 enclosing the fan wheel 17, and also formingthe bearing tube 2, is arranged radially adjacent to the fan wheel 17.The flow divider 18 and the outer part 40 form a diffuser into thepressure space D.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways.

Such variations are not to be regarded as a departure from thedisclosure, and all such modifications are intended to be includedwithin the scope of the disclosure.

1.-11. (canceled)
 12. A bearing arrangement designed as a fixed/floatingbearing for a fan rotor, comprising: a bearing tube, a compressionspring, a shaft arranged coaxially with respect to the bearing tube, andtwo identically formed ball bearings arranged between the bearing tubeand the shaft, each ball bearing has an inner ring and an outer ring;multiple different fit zones are formed axially along the bearing tube,in a first axial fit zone, one of the ball bearings as a fixed bearingis attached by its inner ring on the shaft and its outer ring is fixedwith a press fit on a continuous, shoulder-free portion of the bearingtube, in a second axial fit zone, another of the ball bearings as afloating bearing is attached by its inner ring to the shaft and itsouter ring is axially displaceably arranged with a clearance fit on acontinuous, shoulder-free portion of the bearing tube; the compressionspring is arranged in a third axial fit zone, positioned axially betweenthe ball bearings, the compression spring exerting a preload against theouter rings of the ball bearings to eliminate bearing play of thefloating bearing.
 13. The bearing arrangement according to claim 12,wherein the different fit zones are formed by tolerance zones of aninner diameter of the bearing tube.
 14. The bearing arrangementaccording to claim 12 wherein the third axial fit zone corresponds tothe second axial fit zone.
 15. The bearing arrangement according toclaim 12, wherein an axial fit length L1 of the first fit zone of thefixed bearing is defined as 0.35⋅L1≤D≤0.5⋅L1, wherein D is an innerbearing tube diameter of the bearing tube.
 16. The bearing arrangementaccording to claim 12, wherein an axial fit length L2 of the second fitzone of the floating bearing is defined as 0.35⋅L2≤D≤0.5⋅L2, wherein Dis an inner bearing tube diameter of the bearing tube.
 17. The bearingarrangement according to claim 12, wherein the first and/or the secondfit zone each adjoin axial edge sections of the bearing tube.
 18. Thebearing arrangement according to claim 12, wherein a base material ofthe outer rings of the ball bearings is the same as a material of thebearing tube.
 19. The bearing arrangement according to claim 12, whereinthe outer rings of the ball bearings (3, 6) and the bearing tube areformed of soft magnetic steel.
 20. The bearing arrangement according toclaim 12, wherein a collar is formed on an axial end section of thebearing tube and integral with the bearing tube, which collar comprisesa receiving space for inserting a fan wheel.
 21. The bearing arrangementaccording to claim 12, wherein a separate collar is arranged on an axialend section of the bearing tube, which collar comprises a receivingspace for inserting a fan wheel.
 22. A fan having a bearing arrangementaccording to claim 12.